The fecal shield is a double-edged sword for larvae of a leaf beetle

Abstract

Larvae of some leaf beetles carry masses of feces covering parts or all of the body, which is called a “fecal shield”. In general, the shield is thought to be a defense structure against natural enemies. However, some studies have suggested that defense effectiveness varies depending on the natural enemy. In the present study, we used a fecal retention leaf beetle Ophrida xanthospilota (Coleoptera: Chrysomelidae), and two local generalist predators (an ant, Camponotus japonicus (Hymenoptera: Formicidae) and a stinkbug, Arma custos (Hemiptera: Pentatomidae)) as a system to test the hypothesis that the fecal shield of O. xanthospilota plays different roles in predation behavior of different predators and can provide multiple chemical communication signals in predator-prey interactions. Prey bioassays showed that the fecal shield of O. xanthospilota larvae repelled the ant C. japonicus while attracting the stinkbug A. custos. The results also strongly demonstrated that hexane extracts of the fecal shield significantly repelled C. japonicus, while dichloromethane extracts did not inhibit ant predation. Interestingly, dichloromethane extracts attracted A. custos, but hexane extracts did not. Therefore, we suggest that the fecal shield is a double-edged sword for the larvae of O. xanthospilota. Our results also indicated that the risk-benefit tradeoff of an insect should be estimated at a community level involving multiple enemies (predators and parasites) and herbivores, rather than in a single prey-predator pair.

Fecal Deployment: An Alternative Way of Defensive Host Plant Cardenolide Use by Lilioceris merdigera Larvae

“…The use of host plant compounds for defensive purposes can be regarded as shift of a chemical defense strategy to a higher trophic level (Petschenka and Agrawal 2015 ) at certain costs, representing a seesaw between predator pressure and physiological effects and costs (Züst et al 2018 ; Carlson and Agrawal 2023 ). In the case of fecal defense, the protective advantages are linked to disadvantages like possible attraction of parasites and certain predators (Müller and Hilker 2004 ) such that fecal defense was described as a “double-edged sword” (Huang et al 2023 ). Due to its ability to live on plants with strongly differing specialized metabolites, L. merdigera may pose a future model to better investigate this “evolutionary dilemma” (Müller and Hilker 2000 ) in combination with host plant preferences.…”

Architecture, construction, retention, and repair of faecal shields in three tribes of tortoise beetles (Coleoptera, Chrysomelidae, Cassidinae: Cassidini, Mesomphaliini, Spilophorini)

“…Faecal-based constructions and faecal debris-carrying are widespread behaviours in Chrysomelidae . Chrysomelid faecal-based constructions have been studied in terms of ecological function ( Olmstead and Denno 1992 ; Gómez 1997 , 2004 ; Morton 1997 ; Vencl and Morton 1998a , b , 1999 ; Morton and Vencl 1998 ; Gómez et al 1999 ; Müller and Hilker 1999 , 2001a , b , 2003 , 2004 ; Vencl et al 1999 , 2005 , 2011 ; Nogueira-de-Sá and Trigo 2002 , 2005 ; Bacher and Luder 2005 ; Bottcher et al 2009 ; Huang et al 2022 ). Until now, this faecal building behaviour has been studied in only one chrysomelid, Neochlamisus by Brown and Funk (2005) .…”

“…Others have determined the shields to have mixed effects, deterring some predators yet attracting others ( Müller and Hilker 1999 ; Bacher and Luder 2005 ; Huang et al 2022 ). Certainly, faeces can have chemical signatures that attract enemies ( Van Leerdam et al 1985 ; Agelopoulus et al 1995 ).…”

“…Corpse covers and debris cloaks may provide mechanical protection, from weather or predators (e.g., spiders, lizards), or permit aggressive mimicry towards their prey (e.g., ants, termites). Olfactory cues can mask the predator ( Odihiambo 1958 ; Brandt and Mahsberg 2002 ; Jackson and Pollard 2007 ; Stromberg 2012 ) or may become a secondary signal that attracts enemies ( Agelopoulus et al 1995 ; Benelli et al 2013 ; Huang et al 2022 ).…”